Cisco IOS loadable modules pose hacker risk

Cracker sniffing

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Rootkits and loadable kernel modules which could allow a cracker to obtain administrator level access to routers will become a greater threat as Cisco develops its technology.

That's the warning from Nicolas Fischbach and Sebastien Lacoste, both of the security team of COLT Telecom. Future attacks are also likely to include advanced router protocol attacks, they say.

Network level hacker attacks are less publicised than those against servers but offer a way for crackers to sniff vital information on a network, block or modify traffic or impersonate a party in a conversation.

It's a common misconception among organisations that, providing they have a properly configured firewall, they are immune from attacks. But the increase in intruder compromise and use of routers in attacks belies this myth, and highlights the importance of making network infrastructure secure.

Fischbach and Lacoste fears such attacks will become more powerful with the next development of router software from Cisco, Cisco IOS-NG, which features support for loadable kernel modules in a similar way to Linux.

During a presentation at a recent Black Hat security conference they outlined how it might be possible for a hacker to upload a modified IOS image and start it without a reboot. From that point on a variety of network attacks might be possible.

Russ Spooner, of network security specialists Interrorem, disagreed about the likelihood of uploading a modified IOS image without resetting a router, but doesn't feel this was much of a barrier to attacks.

He agreed that the development of IOS loadable modules, which he didn't feel would be particular hard to develop since IOS is similar BSD, might allow crackers to upload tools that would allow them to take control of networks. These tools could be hidden in the binary code and - unless Cisco set up a strong cryptographic signing regime for modules - could pose a severe risk, he added. ®